Wadie Tadros

Reactions with asymmetric diarylethylenes. Part XV. Dimerisation of 1,1-bis-p-alkoxyphenylethylenes

Dimerisation of 1,1-bis-p-methoxy(or -ethoxy)phenylethylene with hydrogen chloride or bromide, trichloroacetic acid, or glacial acetic acid–sulphuric acid gave 1,1,3,3-tetrakis-p-methoxy(or -ethoxy)phenylbut-1-ene, identified on the basis of synthetic, degradative, and reduction studies and n.m.r. spectral evidence. Chlorination of the dimer gave the corresponding monomer and its chloro-derivative, whereas bromination gave the dibromo-dimer, which could be converted into the corresponding buta-1,3-diene. Iodination gave only the monomer. The mechanism of the reactions with bromine and chlorine is discussed.

Reactions with asymmetric diarylethylenes and diarylethanes. Part XIV. Addition of xanthenyl chloride to the ethylenes

Xanthenyl chloride adds readily to asymmetric diarylethylenes to give after dehydrochlorination, 1,1-bis-(p-substituted phenyl)-2-(xanthen-9-yl)ethylenes. The nature of the para-substituent in the olefinic products has an influence on their reaction with bromine. In the presence of p-alkoxy-groups 1,1-bis-(p-alkoxyphenyl)-2-bromo-2-(xanthen-9-yl)ethylenes are obtained as main products; small quantities of xanthenyl tribromide, 1,1-diaryl-2-bromoethylenes, and xanthen are also isolated. The latter three compounds are the main products when the para-substituents are bromine, chlorine, or hydrogen.The structures of the 1,1-bis-(p-alkoxyphenyl)-2-bromo-2-(xanthen-9-yl)ethylenes were confirmed by (a) ozonolysis and (b) transformation with alcoholic potassium hydroxide into the corresponding allenes [1,1-bis-(p-alkoxyphenyl)-2-(xanthen-9-ylidene)ethylenes].

Reactions with asymmetric diarylethanes and diarylethylenes. Part XIII. Rearrangements of 1,1-dihalogeno-2,2-diarylethanes and the corresponding 1-halogenoethylenes in boiling ethylene glycol, alone or in the presence of sodium 2-hydroxyethoxide

1,1-Dihalogeno-2,2-di-p-tolylethane in boiling ethylene glycol (98%) gave the corresponding 1-halogenoethylene, the corresponding stilbene, the cyclic acetal 1,1-ethylenedioxy-2,2-di-p-tolylethane, 4,4′-dimethyldeoxybenzoin, di-p-tolylacetaldehyde, and 4,4′-dimethylbenzophenone. The last three compounds are also formed when a solution of the acetal in acidified ethylene glycol (98%) is boiled. The 1-halogenoethylene gave the deoxybenzoin and a trace of 1,1-di-p-tolylethylene in boiling ethylene glycol. 1,1-Dichloro-2,2-bis-p-bromophenyl-(or 2,2-bis-p-chlorophenyl)-ethane underwent partial dehydrochlorination.1,1-Dihalogeno-2,2-di-p-tolylethane, and the corresponding 1-halogenoethylene, with sodium 2-hydroxyethoxide in boiling ethylene glycol (98%) gave di-p-tolylacetylene and traces of the cyclic acetal and ditolylacetic acid. 1,1-Dichloro-2,2-bis-p-bromo-(or 2,2-bis-p-chloro)-phenylethane, and the 1-chloroethylene gave the cyclic acetal, 1,1-bis-p-chlorophenyl-2-(2-hydroxyethoxy)ethylene, bis-p-chlorophenylacetic acid, and bis-p-chlorophenylmethane. The 1-bromoethylene gave in addition a trace of bis-p-bromo-(or chloro)-phenylacetylene.

Reactions with asymmetrical diarylethanes and diarylethylenes. Part XII. Reactions of 1,1,1-trihalogeno-2,2-diarylethanes and the corresponding 1,1-dihalogenoethylenes with sodium 2-hydroxyethoxide

When heated to boiling in ethylene glycol with sodium 2-hydroxyethoxide, 1,1,1-tribromo-2,2-di-p-tolyl(or bis-p-chlorophenyl)ethane or the corresponding 1,1-dibromoethylenes gave the 1-bromoethylene, the diarylacetylene, the cyclic acetal of the diarylacetaldehyde, and the diarylacetic acid, in each case. 1,1,1-Trichloro-2,2-di-p-tolylethane or the 1,1-dichloroethylene gave the same products under more drastic conditions, but the corresponding bis-p-chlorophenyl compounds gave mainly bis-p-chlorophenylmethane and bis-p-chlorophenylacetic acid.

Reactions with asymmetrical diarylethylenes and diarylethanes. Part XI. Rearrangement reactions of 1,1-di-p-alkoxyphenyl-2,2-dihalogenoethanes in boiling ethylene glycol alone or in the presence of sodium 2-hydroxyethoxide

1,1-Di-p-alkoxyphenyl-2,2-dibromoethanes are readily converted by boiling ethylene glycol into the corresponding 4,4′-dialkoxystilbenes and the cyclic acetals of 4,4′-dialkoxydiphenylacetaldehydes with the liberation of hydrogen bromide. Longer heating gives the corresponding 4,4′-dialkoxy-diphenylacetaldehydes, -deoxybenzoins, and -benzophenones. The latter three classes are also formed on heating solutions of the acetals in acidified ethylene glycol.The structure of the acetals has been confirmed by their syntheses from 4,4′-dialkoxydiphenylacetaldehydes and ethylene glycol in the presence of hydrogen chloride.Heating the equimolecular quantities of the 1,1-di-p-alkoxyphenyl-2,2-dihalogenoethanes and sodium 2-hydroxyethoxide in ethylene glycol gives the corresponding deoxybenzoins, while increasing the ratio of the reagent gives the acetylenes.